Achieving water release zone for dewatering thick fine tailings based on shearing parameter such as camp number

ABSTRACT

Various techniques are provided in relation to flocculation and/or dewatering of thick fine tailings, with shear conditioning of flocculated tailings material in accordance with a pre-determined shearing parameter, such as the Camp Number. One example method of treating thick fine tailings including dispersing a flocculant into the thick fine tailings to form a flocculating mixture; shearing the flocculating mixture to increase yield stress and produce a flocculated mixture; shear conditioning the flocculated mixture to decrease the yield stress and break down flocs, the shear conditioning being performed in accordance with the pre-determined shearing parameter to produce conditioned flocculated material within a water release zone where release water separates from the conditioned flocculated material. The conditioned flocculated material can then be subjected to dewatering, for example by depositing, thickening or filtering. The design, construction and/or operation of a flocculation pipeline assembly can be facilitated.

REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. patent application Ser. No.14/408,691, filed Dec. 17, 2014, which is the U.S. National Stage ofInternational Application No. PCT/CA2013/050490, filed Jun. 21, 2013,which claims priority from U.S. Provisional Application No. 61/662,695,filed Jun. 21, 2012, the disclosures of which are incorporated in theirentireties herein.

FIELD OF INVENTION

The present invention generally relates to the field of dewatering thickfine tailings.

BACKGROUND

Thick fine tailings derived from mining operations, such as oil sandsmining, are often placed in dedicated disposal ponds for settling. Thesettling of fine solids from the water in tailings ponds is a relativelyslow process. Certain techniques have been developed for dewateringthick fine tailings, such as oil sands mature fine tailings (MFT).Dewatering of thick fine tailings can include contacting the thick finetailings with a flocculant and then depositing the flocculated finetailings in a deposition area where the deposited material can releasewater and eventually dry.

There are various challenges related to flocculating thick fine tailingswith the view of dewatering the flocculated material.

SUMMARY

Various techniques are described herein for enhanced operations withrespect to various aspects of flocculation and/or dewatering of thickfine tailings.

In some implementations, there is provided a method of treating thickfine tailings, comprising:

-   -   flocculating the thick fine tailings comprising the following        flocculation stages:        -   a dispersion stage comprising dispersing a flocculant into            the thick fine tailings to form a flocculation tailings            material;        -   a floc build-up stage comprising shearing the flocculation            tailings material and increasing the yield stress of the            flocculation tailings material; and        -   a floc breakdown stage comprising shearing the flocculation            tailings material under a laminar flow regime and decreasing            the yield stress of the flocculation tailings material            decreases, wherein the floc breakdown stage comprises:            -   imparting a pre-determined amount of shear conditioning                to the flocculation tailings material in accordance with                a Camp Number sufficient that the flocculation tailings                material attains a water release zone wherein release                water separates from the flocculation tailings material;                and    -   depositing the flocculation tailings material that is within the        water release zone onto a sub-aerial deposition area.

In some implementations, the pre-determined amount of shear conditioningis provided by a pipeline assembly.

In some implementations, the pipeline assembly has a configurationdetermined by Camp Number scaling from laboratory scale mixer tests.

In some implementations, the Camp Number scaling comprises: determiningrheological behaviour of a sample flocculation mixture comprising asample of the thick fine tailings and the flocculant in the laboratoryscale mixer; determining a laboratory scale Camp Number sufficient tobring the sample flocculation mixture within a water release zone in thelaboratory scale mixer; determining the Camp Number so as to besubstantially similar to the laboratory scale Camp Number; anddetermining an equivalent pipe length for the pipeline assembly based onthe Camp Number.

In some implementations, the Camp Number is within about 10% of thelaboratory scale Camp Number. In some implementations, the laboratoryscale mixer comprises a paddle mixer.

In some implementations, the step of determining rheological behaviourof the sample flocculation mixture, comprises: determining an optimalflocculant dose range for addition to the sample of the thick finetailings; adding the flocculant into the sample of the thick finetailings within the optimal flocculant dose range, to form a sampleflocculating mixture; imparting dispersive mixing to the sampleflocculating mixture in order to promote dispersion of the flocculantand floc build up, to form a flocculated material; and imparting lowermixing to the flocculated material in order to commence floc breakdownuntil reaching the water release zone; and determining a yield stressresponse over time of the flocculating mixture and the flocculatedmaterial.

In some implementations, the step of determining the Camp Numbercomprises using a Herschel-Bulkley Model.

In some implementations, the pipeline assembly comprises at least onebifurcation into branch lines. In some implementations, the pipelineassembly comprises an in-line mixer having an equivalent pipe lengthvalue. In some implementations, the pipeline assembly consistsessentially of a pipeline.

In some implementations, the process also includes:

-   -   modifying the step of flocculating the thick fine tailings by        changing:        -   properties of the thick fine tailings,        -   type of flocculant; and/or        -   dosage of the flocculant with respect to the thick fine            tailings;    -   determining a new Camp Number and a new pre-determined amount of        shear conditioning for the floc breakdown stage; and    -   imparting the new pre-determined amount of shear conditioning to        the flocculation tailings material sufficient that the        flocculation tailings material is within the water release zone.

In some implementations, the step of imparting the new pre-determinedamount of shear conditioning comprises re-configuring the pipelineassembly to increase or decrease the equivalent pipe length.

In some implementations, the pipeline assembly comprises a plurality oflines for transporting and depositing the flocculation tailings materialonto respective deposition areas, the lines being configured to havesubstantially the same lengths and diameters.

In some implementations, the pipeline assembly comprises a plurality oflines for transporting and depositing the flocculation tailings materialonto respective deposition areas, each of the lines being configured tohave different lengths and/or different diameters, and being selected toreceive a corresponding flow of the flocculation tailings material inaccordance with a corresponding pre-determined amount of shearconditioning.

In some implementations, the Camp Number and the pre-determined amountof shear conditioning are provided so as to achieve a water release peakrange within the water release zone.

In some implementations, the thick fine tailings comprise mature finetailings. In some implementations, the mature fine tailings are derivedfrom oil sands. In some implementations, the thick fine tailings areretrieved from a tailings pond or from a separation unit of anextraction operation.

In some implementations, there is provided a method of treating thickfine tailings, comprising:

-   -   dispersing a flocculant into the thick fine tailings to produce        a flocculation tailings material;    -   pipeline conditioning the flocculation tailings material to        impart:        -   sufficient shear to build up flocs and reach a peak yield            stress of the flocculation tailings material; and        -   a pre-determined amount of shear conditioning to the            flocculation tailings material in accordance with a Camp            Number sufficient that the flocculation tailings material            having a laminar flow regime decreases in yield stress from            the peak yield stress and reaches a water release zone            wherein release water separates from the flocculation            tailings material; and    -   depositing the flocculation tailings material that is within the        water release zone onto a sub-aerial deposition area.

In some implementations, there is provided a method of configuring apipeline assembly for transporting and conditioning a flocculated thickfine tailings material, comprising:

-   -   determining under laminar conditions a laboratory scale Camp        Number for a sample of flocculated thick fine tailings        sufficient to achieve floc breakdown and water release; and    -   providing the pipeline assembly with a configuration so as to        provide a substantially similar Camp Number as the laboratory        scale mixer Camp Number with respect to the flocculated thick        fine tailings material having a laminar flow regime through the        pipeline assembly.

In some implementations, there is provided a method of treating thickfine tailings, comprising:

-   -   dispersing a flocculant into the thick fine tailings to form a        flocculating mixture;    -   shearing the flocculating mixture to increase a yield stress of        the flocculating mixture and build up flocs, thereby producing a        flocculated mixture;    -   shear conditioning the flocculated mixture to decrease the yield        stress of the flocculated mixture and break down flocs, wherein        the shear conditioning is performed in accordance with a        pre-determined shearing parameter sufficient to produce a        conditioned flocculated material that is within a water release        zone wherein release water separates from the conditioned        flocculated material; and    -   dewatering the conditioned flocculated material while within the        water release zone.

In some implementations, the step of dewatering comprises depositing theconditioned flocculated material onto a sub-aerial deposition area.

In some implementations, the step of dewatering comprises supplying theconditioned flocculated material into a separation apparatus to separatethe release water from a water-reduced tailings material.

In some implementations, there is also the step of empirically derivingthe pre-determined shearing parameter.

In some implementations, the pre-determined shearing parameter comprisesor consists of shear rate and residence time variables.

In some implementations, the pre-determined shearing parameter comprisesa dimensionless number.

In some implementations, the step of empirically deriving thepre-determined shearing parameter comprises laboratory experimentation.

In some implementations, the step of empirically deriving thepre-determined shearing parameter comprises: determining rheologicalbehaviour of a sample flocculation mixture comprising a sample of thethick fine tailings and the flocculant in a laboratory scale mixer,wherein the sample flocculation mixture increases in yield stress toform a sample flocculated mixture and then decreases in yield stressunder shearing conditions; determining a laboratory scale shearingparameter sufficient to bring the sample flocculated mixture within awater release zone in the laboratory scale mixer; and determining thepre-determined shearing parameter so as to be substantially similar tothe laboratory scale shearing parameter.

In some implementations, there is also the step of determining anequivalent pipe length and diameter for a pipeline assembly based on thepre-determined shearing parameter in order to provide the shearconditioning.

In some implementations, the laboratory scale mixer comprises a paddlemixer.

In some implementations, the step of determining rheological behaviourof the sample flocculation mixture, comprises: determining an optimalflocculant dose range for addition to the sample of the thick finetailings; adding the flocculant into the sample of the thick finetailings sample at the optimal flocculant dose range, to form a sampleflocculating mixture; imparting dispersive mixing to the sampleflocculating mixture in order to promote dispersion of the flocculantand floc build up, to form the sample flocculated mixture; impartinglower mixing to the sample flocculated mixture in order to commence flocbreakdown until reaching the water release zone; and determining a yieldstress response over time of the flocculating mixture and theflocculated material.

In some implementations, the pre-determined shearing parameter comprisesa Camp Number. In some implementations, the pre-determined shearingparameter consists of a Camp Number.

In some implementations, the shear conditioning the flocculated mixtureis performed under laminar flow conditions.

In some implementations, the shear conditioning is provided by apipeline assembly.

In some implementations, the pipeline assembly is provided with a lengthand a diameter sufficient to impart the shear conditioning to theflocculated mixture in accordance with the pre-determined shearingparameter.

In some implementations, there is provided a treatment system fortreating thick fine tailings, comprising:

-   -   a dispersion and floc build-up assembly for dispersing a        flocculant into the thick fine tailings to form a flocculating        mixture and subjecting the flocculating mixture to shear to        increase a yield stress of the flocculating mixture and build up        flocs, thereby producing a flocculated mixture;    -   a pipeline conditioning assembly sized and configured for        subjecting the flocculated mixture to an amount of shear        conditioning in accordance with a pre-determined shearing        parameter sufficient to decrease the yield stress of the        flocculated mixture and produce a conditioned flocculated        material that is within a water release zone wherein release        water separates from the conditioned flocculated material; and    -   a dewatering unit for receiving the conditioned flocculated        material while within the water release zone, for producing        release water and dewatered tailings material.

In some implementations, the pipeline conditioning assembly is sized andconfigured such that the flocculated mixture has a laminar flow regimeand the pre-determined shearing parameter is a pre-determined CampNumber.

In some implementations, the pipeline conditioning assembly is sized tohave a pipe length and diameter for providing the pre-determined CampNumber.

In some implementations, the system also includes a test kit fordetermining the pre-determined Camp Number.

In some implementations, the test kit comprises: a vessel for receivinga sample mixture comprising a sample of the thick fine tailings and theflocculant; a mixing element for mixing the sample mixture within thevessel; a yield stress measurement device for measuring yield stress ofthe sample mixture during the mixing; a timer for measuring the timeduring the mixing; a shear rate measurement device for measuring theshear rate of the mixing; and water release detector for determiningwhen the sample mixture achieves the water release zone where waterseparates from the sample mixture.

In some implementations, the test kit further comprises a recordingdevice for recording the yield stress and the time of the sample mixturefor determining yield stress versus time relationship.

In some implementations, the dispersion and floc build-up assemblycomprises a mixer for dispersing the flocculant into the thick finetailings to form the flocculating mixture; and a shearing assembly forsubjecting the flocculating mixture to shear to produce the flocculatedmixture. In some implementations, the mixer comprises an in-lineco-annular mixer.

In some implementations, the first shearing assembly comprises a pipesection in fluid communication with the mixer for providing shear in theform of pipe flow shearing.

In some implementations, the pipeline conditioning assembly consistsessentially of piping and has a pipe length and diameter sufficient toprovide the amount of shear conditioning in accordance with thepre-determined shearing parameter.

In some implementations, the pipeline conditioning assembly comprises anin-line shear unit having an equivalent pipe length, such that thepipeline conditioning assembly has a total equivalent pipe lengthsufficient to provide the amount of shear conditioning in accordancewith the pre-determined shearing parameter.

In some implementations, there is provided a method of designing apipeline assembly for transporting and conditioning a flow offlocculated thick fine tailings material to a dewatering unit,comprising:

-   -   shearing a sample of flocculated thick fine tailings material        and determining a sample shearing parameter comprising residence        time and shear rate sufficient to bring the sample within a        water release zone where release water separates from the        sample; and    -   configuring the pipeline assembly so as to have a pipe length        and diameter providing a pipeline shearing parameter that is        substantially similar to the sample shearing parameter.

In some implementations, the shearing of the sample of flocculated thickfine tailings material is performed under laminar conditions and theflow of the flocculated thick fine tailings material has a laminar flowregime.

In some implementations, the sample shearing parameter comprises asample Camp Number and the pipeline shearing parameter comprises apipeline Camp Number.

In some implementations, the shearing of the sample of flocculated thickfine tailings material is performed in a laboratory scale mixer. In someimplementations, the laboratory scale mixer comprises a paddle mixer.

In some implementations, the method also includes: adding a flocculantto a sample of thick fine tailings to produce a sample flocculatingmixture; and subjecting the sample flocculating mixture to shear so asto build up flocs and increase yield stress to a peak yield stress levelto produce the sample of flocculated thick fine tailings material.

In some implementations, the configuring of the pipeline assemblycomprises providing at least one bifurcation into branch lines. In someimplementations, the configuring of the pipeline assembly comprisesproviding an in-line mixer having an equivalent pipe length value.

In some implementations, the method also includes shearing multiplesamples of the flocculated thick fine tailings material and determiningmultiple corresponding sample shearing parameters sufficient to bringthe sample within a water release zone where release water separatesfrom the sample; and configuring the pipeline assembly to providemultiple line sections having different lengths and/or diameters forimparting corresponding pipeline shearing parameters that aresubstantially similar to the respective sample shearing parameters.

In some implementations, the thick fine tailings and the sample comprisemature fine tailings. In some implementations, the mature fine tailingsand the sample are derived from oil sands. In some implementations, thethick fine tailings and the sample are retrieved from a tailings pond orfrom a separation unit of an extraction operation.

In some implementations, there is provided a method of dewatering thickfine tailings, comprising:

-   -   flocculating the thick fine tailings to produce a flocculated        thick fine tailings material;    -   shear conditioning the flocculated thick fine tailings material        in a pipeline assembly having a pipe length and diameter sized        and configured according to a pipeline shearing parameter that        is substantially similar to a pre-determined sample shearing        parameter comprising residence time and shear rate sufficient to        bring a sample of the flocculated thick fine tailings material        within a water release zone where release water separates from        the sample, the pipeline assembly producing a conditioned        flocculated material within the water release zone; and    -   dewatering the conditioned flocculated material while within the        water release zone.

In some implementations, the flocculating step is performed in-line andcomprises dispersing a flocculant into the thick fine tailings to form aflocculating mixture and shearing the flocculating mixture to build upflocs and produce the flocculated thick fine tailings material.

In some implementations, the pre-determined sample shearing parameter isdetermined under laminar conditions and the shear conditioning of theflocculated thick fine tailings material is performed in a laminar flowregime in the pipeline assembly.

In some implementations, the pre-determined sample shearing parameter isa sample Camp Number.

In some implementations, the pre-determined sample shearing parameter isdetermined by mixing a flocculant with a sample thick fine tailings toproducing a sample flocculating mixture under turbulent conditions toform the sample of the flocculated thick fine tailings material having apeak yield stress, and then shearing the sample of the flocculated thickfine tailings material under laminar conditions until the water releasezone.

In some implementations, the laboratory scale mixer comprises a paddlemixer.

In some implementations, there is provided a method of dewatering thickfine tailings, comprising:

-   -   flocculating the thick fine tailings to produce a flocculated        thick fine tailings material;    -   shear conditioning the flocculated thick fine tailings material        in a pipeline assembly having a pipe length and diameter sized        substantially independent of flow rate of the flocculated thick        fine tailings material and according to a pre-determined        pipeline shearing parameter determined under laminar conditions        and comprising residence time and shear rate, the pipeline        assembly producing a conditioned flocculated material within the        water release zone;    -   flowing the flocculated thick fine tailings material in the        pipeline assembly to have a laminar flow regime; and    -   dewatering the conditioned flocculated material while within the        water release zone.

In some implementations, the flocculating step is performed in-line andcomprises dispersing a flocculant into the thick fine tailings to form aflocculating mixture and shearing the flocculating mixture to build upflocs and produce the flocculated thick fine tailings material.

In some implementations, the pre-determined sample shearing parameter isa sample Camp Number.

In some implementations, the pre-determined sample shearing parameter isdetermined by mixing a flocculant with a sample thick fine tailings toproducing a sample flocculating mixture under turbulent conditions toform the sample of the flocculated thick fine tailings material having apeak yield stress, and then shearing the sample of the flocculated thickfine tailings material under laminar conditions until the water releasezone.

In some implementations, the laboratory scale mixer comprises a paddlemixer.

In some implementations, the pipeline assembly consists essentially of apipe.

In some implementations, there is provided a method of dewatering thickfine tailings, comprising:

-   -   adding a flocculant into the thick fine tailings to produce a        flocculation tailings material;    -   shear conditioning the flocculation tailings material in a        pipeline assembly to produce a conditioned flocculated material        within a water release zone wherein release water separates from        the conditioned flocculated material;    -   providing sufficient mixing of the flocculant and the thick fine        tailings prior to the shear conditioning, so as to enable the        pipeline assembly to have a pipe length based on Camp Number        scaling to achieve the water release zone; and dewatering the        conditioned flocculated material within the water release zone.

In some implementations, the step of adding the flocculant is performedin-line.

In some implementations, the step of providing sufficient mixing isperformed in-line.

In some implementations, the step of providing sufficient mixing isperformed to increase a yield stress of the flocculation tailingsmaterial to a peak yield stress level.

In some implementations, the step of adding the flocculant is performedunder turbulent flow conditions.

In some implementations, the step of providing sufficient mixingcomprises subjecting the flocculation tailings material to turbulentflow conditions to build up flocs until reaching laminar flow conditionsprior to the shear conditioning.

In some implementations, the Camp Number scaling comprises: mixing asample of the thick fine tailings with the flocculant under turbulentconditions to produce a sample flocculated mixture; shearing the sampleflocculated mixture under laminar conditions to determine a Camp Numberfor achieving the water release zone in the sample; and providing thepipeline assembly with a length and a diameter for providing theflocculating tailings material with an amount of shear according to theCamp Number.

In some implementations, the mixing a sample of the thick fine tailingswith the flocculant is performed in a laboratory scale mixer.

In some implementations, the shearing of the sample flocculated mixtureis performed in the laboratory scale mixer.

In some implementations, the laboratory scale mixer comprises a paddlemixer.

In some implementations, the pipeline assembly comprises at least onein-line shear device having an equivalent pipe length.

In some implementations, the pipeline assembly consists essentially of apipe.

In some implementations, there is provided a treatment system fortreating thick fine tailings, comprising:

-   -   an in-line injector for injecting a flocculant into a turbulent        flow of the thick fine tailings to form a flocculating mixture;    -   a floc build-up pipeline assembly in fluid communication with        the in-line injector for receiving the flocculating mixture and        subjecting the flocculating mixture to shear to increase a yield        stress of the flocculating mixture and build up flocs, thereby        producing a flocculated mixture;    -   a floc breakdown pipeline assembly in fluid communication with        the floc build-up pipeline assembly for receiving the        flocculated mixture, the floc breakdown pipeline assembly being        sized and configured for subjecting the flocculated mixture to        an amount of shear conditioning under laminar conditions in        accordance with a pre-determined shearing parameter sufficient        to decrease the yield stress of the flocculated mixture and        produce a conditioned flocculated material that is within a        water release zone wherein release water separates from the        conditioned flocculated material, the pre-determined shear        parameter comprising residence time and shear rate in laminar        conditions; and    -   a dewatering unit for receiving the conditioned flocculated        material while within the water release zone, for producing        release water and dewatered tailings material.

In some implementations, the pre-determined shearing parameter is apre-determined Camp Number.

In some implementations, the floc breakdown pipeline assembly is sizedto have a pipe length and diameter for providing the pre-determined CampNumber.

In some implementations, the floc breakdown pipeline assembly consistsessentially of piping and has a pipe length and diameter sufficient toprovide the amount of shear conditioning in accordance with thepre-determined shearing parameter.

In some implementations, the floc breakdown pipeline assembly comprisesan in-line shear unit having an equivalent pipe length, such that thepipeline conditioning assembly has a total equivalent pipe lengthsufficient to provide the amount of shear conditioning in accordancewith the pre-determined shearing parameter. In some implementations, thein-line shear unit comprises a static mixer.

In some implementations, the pre-determined shearing parameter isvariable and the system further comprises an additional pipe sectionremovably mountable to an outlet end of the floc breakdown pipelineassembly in order to vary the amount of shear conditioning under laminarconditions imparted to the flocculated tailings material in accordancewith the pre-determined shearing parameter.

In some implementations, the floc breakdown pipeline assembly comprises:a first pipeline having a first diameter and a first length sufficientfor providing the amount of shear conditioning, and configured to supplythe conditioned flocculated material to a first dewatering unit; and asecond pipeline having a second diameter smaller than the first diameterand a second length smaller than the first length providing the amountof shear conditioning, and configured to supply the conditionedflocculated material to a second dewatering unit located closer than thefirst.

In some implementations, the thick fine tailings comprise mature finetailings. In some implementations, the mature fine tailings are derivedfrom oil sands. In some implementations, the thick fine tailings areretrieved from a tailings pond or from a separation unit of anextraction operation.

It should also be noted that various features and implementationsdescribed above may be combined with one or more other features orimplementations described above or herein.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a block diagram of a dewatering operation.

FIG. 2 is a graph of yield stress and net water release versus time inmixer.

FIG. 3 is a graph of yield stress versus time in mixer.

FIG. 4 is a graph of yield stress versus time in mixer.

FIG. 5 is a graph of yield stress versus time in mixer.

FIG. 6 is a schematic of the geometry and stress profile in a large gapconcentric system for a fluid with a yield stress.

FIG. 7 is a series of graphs of shear stress versus shear rate fordifferent fluid models.

FIG. 8 is a block diagram of a flocculant dosing test procedure.

FIG. 9 is another block diagram of a dewatering operation.

DETAILED DESCRIPTION

Dewatering operations for treating thick fine tailings may includeflocculation of the thick fine tailings followed by pipelineconditioning and deposition of the flocculated material onto asub-aerial deposition site where the deposited material can dewater anddry. Various techniques are described herein for dewatering thick finetailings by providing shear conditioning based on a pre-determinedshearing parameter, such as a Camp Number that may be empiricallyderived from laboratory mixer tests, to impart sufficient shear so thatthe flocculated thick fine tailings material is within a water releasezone where release water separates from the material. A pipelineassembly for transporting and conditioning the flocculated thick finetailings material may be sized and configured in accordance with thepre-determined shear parameter, for facilitated design, construction andoperation of dewatering facilities.

“Thick fine tailings” may be considered as suspensions derived from amining operation and mainly include water and fines. The fines are smallsolid particulates having various sizes up to about 44 microns. Thethick fine tailings have a solids content with a fines portionsufficiently high such that the fines tend to remain in suspension inthe water and the material has slow consolidation rates. Moreparticularly, the thick fine tailings may have a ratio of coarseparticles to the fines that is less than or equal to 1. The thick finetailings has a fines content sufficiently high such that flocculation ofthe fines and conditioning of the flocculated material can achieve a twophase material where release water can flow through and away from theflocs. For example, thick fine tailings may have a solids contentbetween 10 wt % and 45 wt %, and a fines content of at least 50 wt % ona total solids basis, giving the material a relatively low sand orcoarse solids content. The thick fine tailings may be retrieved from atailings pond, for example, and may include what is commonly referred toas “mature fine tailings” (MFT).

“MFT” refers to a tailings fluid that typically forms as a layer in atailings pond and contains water and an elevated content of fine solidsthat display relatively slow settling rates. For example, when wholetailings (which include coarse solid material, fine solids, and water)or thin fine tailings (which include a relatively low content of finesolids and a high water content) are supplied to a tailings pond, thetailings separate by gravity into different layers over time. The bottomlayer is predominantly coarse material, such as sand, and the top layeris predominantly water. The middle layer is relatively sand depleted,but still has a fair amount of fine solids suspended in the aqueousphase. This middle layer is often referred to as MFT. MFT can be formedfrom various different types of mine tailings that are derived from theprocessing of different types of mined ore. While the formation of MFTtypically takes a fair amount of time (e.g., between 1 and 3 years undergravity settling conditions in the pond) when derived from certain wholetailings supplied form an extraction operation, it should be noted thatMFT and MFT-like materials may be formed more rapidly depending on thecomposition and post-extraction processing of the tailings, which mayinclude thickening or other separation steps that may remove a certainamount of coarse solids and/or water prior to supplying the processedtailings to the tailings pond.

In some implementations, the thick fine tailings are MFT derived from amining operation, for example, an oil sands mining operation. Forillustrative purposes, some implementations described below may bedescribed in the context of MFT or oil sands MFT, but it should beunderstood that other implementations can be used for thick finetailings derived from other sources.

General Dewatering Operations

Before describing various techniques related to the flocculation andconditioning of the dewatering operation, an example of an overalldewatering operation will be described in general terms with referenceto FIG. 1.

Referring to FIG. 1, in some implementations, the dewatering operationmay include providing thick fine tailings from a tailings source 100,which may be a tailings pond for example, from which a flow of tailings102 is retrieved by dredge or another type of pumping arrangement. Thetailings 102 may then be subjected to pre-treatments, such as screeningand/or pre-shearing in one or more pre-treatment units 104, forproducing a pre-treated tailings flow 106 that is then supplied to achemical addition unit 108 for contacting and mixing with a dewateringchemical 110, such as a flocculant. Once the thick fine tailings aremixed with the flocculant 110, a flocculation tailings material 112 maybe pipelined through a transportation and conditioning assembly 114 andthen discharged onto a deposition site 116 for water release and drying.In some implementations, the transportation and conditioning assemblymay be in the form of a pipeline having certain dimensions andconfiguration. The transportation and conditioning assembly may includemultiple piping sections as well as one or more in-line shear devices.The “flocculation tailings material” 112 may be considered as a mixtureof flocculant and thick fine tailings that is in a state of flocculatingor has been substantially flocculated and may be experiencing flocbreakdown, as will be explained in further detail below. Thetransportation and conditioning assembly 114 may include an upstreamfloc build-up assembly that handles the material while in a state offlocculating and building up flocs, and a downstream floc breakdownassembly that handles the flocculated material while the flocs are beingpartially broken down. The transportation and conditioning assembly 114may consist essentially of a pipeline such that the floc build-up andfloc breakdown assemblies are part of the same overall pipeline. Oncedeposited, the release water may flow away from the flocculated solidmatrix and be recovered by a water recovery assembly 118 for recyclinginto mining operations, extraction operations, water treatmentfacilities or other operations requiring process water.

The transportation and conditioning assembly 114 is configured fortransporting and conditioning the flocculation tailings material 112from the chemical addition unit 108 to the deposition site 116. Inparticular, the floc breakdown assembly may be configured and operatedin accordance with a pre-determined shear parameter, such as the CampNumber, which will be described further below.

Referring to FIG. 9, it should also be noted that the dewatering systemmay include various assemblies including a dispersion assembly, a flocbuild-up assembly, a floc breakdown assembly and a dewatering unit. Insome implementations, the dispersion, floc build-up and floc breakdownassemblies include pipelines, such that the flocculant is added in-lineand the flocculation tailings material is then subjected to conditioningfor floc build-up and breakdown in the pipeline section. The dewateringunit may include a sub-aerial deposition site or other types ofdewatering units (e.g., a thickener or a filter apparatus) that impart arelatively small amount of shear to the material.

Operating within Water Release Zone

In general, after floc build-up the flocculated tailings material may behandled and conditioned in accordance with a pre-determined shearparameter, such as a Camp Number, such that the flocculated tailingsmaterial is conditioned and then dewatered (e.g., deposited) in a stateenabling elevated water release. The relevance of proper handling topromote elevated water release and of the shear parameter will bedescribed in greater detail below.

The shear parameter may be considered as a parameter that represents theamount of shear to be imparted to the flocculation tailings materialafter floc build-up and prior to a dewatering step, such as depositiononto a sub-aerial dewatering site. The shear imparted to theflocculation tailings material has an impact on the development andbreakdown of the flocculated matrix. One example of a shear parameter isthe Camp Number. The Camp Number is a dimensionless number thatgenerally represents the amount of shear imparted over a certain timeinterval to a fluid undergoing a flocculation process. The Camp Numberis the product of a shear rate (i.e., velocity gradient “G” which hasthe units of reciprocal seconds) imparted to the fluid, and the timeduring which the fluid is subjected to that shear rate. Thus, anelevated Camp Number means that the fluid is subjected to an elevatedamount of shear, which may be due to high shear rate, high shearing timeor both. In other words, a given Camp Number may be obtained byproviding high shear rate over a shorter time interval or a lower shearrate over a longer time interval. As will be explained further below,the pre-determined shear parameter, such as a Camp Number, may be usedfor dimensioning and/or operating the dewatering system such that theflocculated tailings material is subjected to an amount of shear toachieve sufficient floc breakdown such that the flocculated matrix is ina state of high water permeability when deposited or subjected to otherdewatering steps.

Referring to FIG. 2, with reference to an example of tailingsflocculation, the rheological evolution of thick fine tailings that issubjected to flocculation may include certain stages:

-   -   (a) A dispersion stage where a flocculation reagent is rapidly        mixed into the thick fine tailings and the flocculation begins,        forming the flocculation tailings material.    -   (b) A floc build-up stage where the flocculation tailings        material increases in yield stress. In this stage, the        flocculation tailings material may be considered as a        flocculating material. As can be seen in FIG. 2, the        flocculation tailings material reaches a peak yield stress. Up        to and around this peak yield stress the flocculation tailings        material may be said to be “under-mixed” because insufficient        mixing or conditioning has been performed to begin to breakdown        the flocculated matrix and allow increased water release. FIG. 2        shows that the water release is effectively nil up to a certain        point just after the peak yield stress, after which the water        release increases up to an initial maximum. Within this floc        build-up and under-mixed stage, the flocculation tailings        material can resemble a gel state material and this stage also        becomes smaller with improved dispersion of the flocculant into        the thick fine tailings.    -   (c) A floc breakdown stage where the flocculation tailings        material decreases in yield shear stress. This stage includes a        “water release zone” where water is released from the        flocculated matrix. FIGS. 2 and 5, for example, illustrate the        water release zone beginning at a certain point within the floc        breakdown stage, after the peak water release, and spanning a        certain mixing time interval over which the water release        gradually decreases. In this stage, the flocculated matrix takes        on a more permeable state and water is released within the water        release zone.    -   (d) An over-shear zone, which is avoided, where the flocs are        broken down to a point that the material generally returns to a        similar state as the initial thick fine tailings. Little to no        water can release from the broken down flocculation matrix.

In order to facilitate efficient dewatering operations, it is desirablethat the flocculation tailings material be deposited while within thewater release zone. Improved performance may also be achieved bymodelling or predicting the conditioning that is sufficient to achieveconsistent operation within the water release zone.

In this regard, FIGS. 3 and 4 illustrate that different tailingscharacteristics and/or flocculant characteristics may results indifferent rheological behavior in response to similar shearconditioning.

FIG. 3 illustrates the static yield stress response of a flocculationtailings material for different MFT samples having differentclay-to-water ratios (CWR) from 0.23 to 0.42. Note that the static yieldstress response generally increases with higher CWR thick fine tailings.

FIG. 4 schematically illustrates different water release zones (in hashmarks) for three different flocculation mixtures A, B and C, which maybe caused by different flocculant type, different flocculant dosingand/or different tailings properties, for example. It can be seen thatthe water release zone may initiate at different times and correspondingshear conditioning levels, and can occupy different intervals. The useof different flocculants on the same MFT can also result in differentrheological behavior of the flocculation tailings material. Inparticular, achieving the water release zone may require more or lessshear for a given flocculant and the water release zone may also besmaller or larger for a given flocculant, for example.

Flocculation modelling has improved understanding of floc developmentand breakdown in the flocculation tailings material. A flocculationmodel has been developed and some aspects thereof will be described ingreater detail below.

In the flocculation model, it may be assumed that rapid and effectivedispersion occurs in stage (a). Regarding stage (a), rapid dispersioncan aid in the efficient mixing of the flocculant into the tailings andeffective floc build-up. Rapid dispersion may be achieved using a numberof configurations and devices, some of which are described in co-pendingCanadian applications 2,701,317 and 2,705,055. An in-line co-annularflocculant injection arrangement may be used and has been shown toprovide effective dispersion. Various other mixing devices may also beused. In addition, a thick fine tailings flow rate above a minimumthreshold may also be provided in order to facilitate effectivedispersion of the flocculant into the thick fine tailings. In general,the thick fine tailings may be provided with a turbulent flow regimeupon contact with the flocculant. When the flocculant is added to thethick fine tailings in-line, the turbulent flow regime may be enabled byproviding sufficiently high flow rate for a given pipe diameter andfluid properties (e.g., density and viscosity) and/or a sufficientlysmall pipe diameter for a given flow rate and fluid properties, forexample. When the flocculant is added to the thick fine tailings usingother types of mixers, which may include static or mobile mixingelements, the mixer may be sized and operated to enable the turbulentmixing regime to enable rapid dispersion.

Assuming rapid initial dispersion, facilitated by providing a turbulentflow regime, the flocculation model can be split into two sections:build-up and breakdown. FIG. 5 illustrates example floc build-up andfloc breakdown stages.

The floc build-up stage can be modelled by computational fluid dynamics(CFD). The peak yield stress is the point where substantially all of thepolymer flocculant has been mixed into the thick fine tailings. Thisbuild-up stage may be dependent on the injector design, flow rates andviscosities of the two fluids (i.e., tailings and flocculant). In someimplementations, the build-up stage may occur within a floc build-upassembly that may be a floc build-up pipeline section downstream fromthe injection point of the flocculant. The floc build-up pipelinesection may also include in-line shear devices, for example when ashorter pipeline section is desired. In some implementations, the flocbuild-up stage may at least partially occur within a tank mixer in whichthe flocculant is added and mixed. In the floc build-up stage, the flowregime of the flocculation tailings material may transition from aturbulent regime to a laminar regime due to the thickening effect of theflocculation.

The floc breakdown stage can be modeled or determined by considerationof a shearing parameter, such as the Camp Number. In the breakdownstage, the flocculation tailings material may be provided with a laminarflow regime. The laminar flow regime may be enabled by providingsufficiently low flow rate for a given pipe diameter and fluidproperties (e.g., density, viscosity, yield stress, etc.) and/or asufficiently large pipe diameter for a given flow rate and fluidproperties. It should also be noted that the flocculation tailingsmaterial entering the breakdown stage has a well-developed flocculatedmatrix, which facilitates the laminar flow regime due to the elevatedviscosity of the material. In some scenarios, the pipeline sections usedto supply the thick fine tailings and to condition the flocculationtailings material have substantially the same diameter, and in suchscenarios the Reynolds Number (Re=ρvD/μ, where ρ is the density of thefluid, v is the mean velocity of the fluid, D is the hydraulic diameterof the pipe for flow in a pipe, and μ is the dynamic viscosity of thefluid) of the flocculation tailings material decreases mainly due to anincrease in the viscosity of the material compared to the thick finetailings prior to flocculation. Thus, the flow rate and the dimensionsof the overall dewatering system (e.g., units and piping) may be suchthat the fluid has a turbulent flow regime prior to and in theflocculant dispersion stage, the fluid transitions from a turbulent to alaminar flow regime during the floc build-up stage, and the fluid has alaminar flow regime in the breakdown stage.

In some implementations, the floc breakdown assembly that transports alaminar flow of the flocculation tailings material within the breakdownstage may be dimensioned based on the Camp Number. The floc breakdownassembly may consist essentially of a pipeline, which may facilitateconstruction, design and maintenance compared to more complex equipmentsetups. The breakdown stage may be modeled based on the Camp Number,where the total amount of shear imparted to the flocculated material issufficient to achieve the water release zone upon deposition of thematerial. The Camp Number can be used to determine the desirable pipediameter and length for the laminar flow of the flocculated tailingsmaterial within the breakdown stage.

In addition, the floc breakdown assembly may be provided based on theCamp Number and independent of the flow rate of the flocculated tailingsmaterial. Considering a given pipe diameter and length, material withhigh flow rates will be subjected to high shear rates but for shorttimes while material with low flow rates will subjected to lower shearrates but for longer times; the overall shear experienced by thematerial is substantially the same for the two cases. By way of example,a given Camp Number may be achieved by providing a small pipe diameterand a short pipe length, or by providing a larger pipe diameter and alonger pipe length. The flow rate of the flocculated tailings materialmay nevertheless be considered in the dimensioning of the breakdownassembly (e.g., the breakdown pipeline section) in order to provide thelaminar flow regime.

The breakdown stage can thus be designed and controlled based on theCamp Number, which is fixed for a given length and diameter of pipe. Thebreakdown stage can also be designed and controlled relativelyindependently of flow rate of the material that has a laminar flowregime.

As the thick fine tailings feed type modifies the initial mixingparameters and Camp Number required for achieving the water releasezone, each dewatering system can be set up with a floc breakdownassembly (e.g., a pipeline configuration having pipe dimensionsincluding length(s) and diameter(s) of one or more pipe sections)suitable for the range of thick fine tailings feeds it may receive. Itshould be noted that the floc breakdown assembly may consist essentiallyof a pipeline configuration, which may include one or more pipe sectionseach having a corresponding pipe length and diameter that may be thesame or different for each pipe section. The pipeline configuration ofthe floc breakdown pipeline section may be provided so as to impart anamount of shear according to a pre-determined shear parameter (e.g.,Camp Number). The floc breakdown assembly may include in-line sheardevices, such as static mixers and the like, that may impart shear andmay be considered as having an equivalent pipe length for the design andoperation of the system.

In some implementations, the method of treating thick fine tailings,such as MFT that may be derived from oil sands mining or other types ofmining, includes flocculating the MFT in a flocculant dispersion stage,a floc build-up stage and a floc breakdown stage. The floc breakdownstage includes imparting a pre-determined amount of shear conditioningto the flocculation tailings material in accordance with a shearingparameter, such as the Camp Number, sufficient that the flocculationtailings material is within the water release zone. The method may alsoinclude depositing the flocculation tailings material within the waterrelease zone, for example onto a sub-aerial deposition area.

The pre-determined amount of shear conditioning in the floc breakdownstage may be provided by a floc breakdown pipeline assembly that isconfigured for that purpose. The floc breakdown pipeline assembly may besized, configured and constructed based on the pre-determined shear orretrofitted in order to add or remove pipe sections, thereby adjustingoverall pipe length to achieve the desired Camp Number. The flocbreakdown pipeline assembly may include in-line shear devices, such asan in-line mixer, having an equivalent pipe length value that is takeninto account for the pre-determined shear. The floc breakdown pipelineassembly may also consist essentially of a pipeline with associatedvalves and fittings as needed for operation, without any other in-lineshear devices.

The pre-determined amount of shear conditioning may be provided by CampNumber scaling from laboratory scale mixer tests up to the pipelineassembly. Implementations of the Camp Number scaling methodology will befurther described below.

In some implementations, the floc breakdown pipeline assembly mayinclude a plurality of lines for transporting and depositing theflocculation tailings material into respective deposition areas, atleast some of the lines being configured to have substantially the samelength and diameter. The floc breakdown pipeline assembly may beconfigured to provide substantially equivalent shear conditioningthrough each line that feeds a corresponding deposition area or otherdewatering unit. This enables treatment of a same thick fine tailingssource with alternating or rotating deposition into different depositionareas, which is typically required to allow material deposited into agiven area time to dewater and dry before additional flocculationtailings material is deposited. Various pipeline configurations arepossible in this regard.

In some implementations, the floc breakdown pipeline assembly may haveat least some lines that are configured to have different lengths and/ordifferent diameters. In one scenario, the floc breakdown pipelineassembly may include smaller diameter and shorter length pipe sectionsfor transport and deposition into proximate deposition areas, as well aslarger diameter and longer length pipe sections for transport anddeposition into more distant deposition areas, thereby providingsubstantially similar total shear according to a pre-determined shearparameter, such as the Camp Number, to the flocculated materialdeposited at both proximate and distant locations. In another scenario,the lines have different lengths or diameters, and one or more of suchlines can be selected to receive a flow of the flocculation tailingsmaterial in accordance with a corresponding pre-determined amount ofshear conditioning that should be imparted to that flow of material. Forinstance, there may be longer and shorter lines, and the longer linesmay be used when the pre-determined shear is higher and the shorterlines would be used when the pre-determined shear is lower, therebyimparting an appropriate amount of shear to different flocculationtailings materials. There may also be lines of smaller diameter andlines of larger diameter for performing similar selective shearing ondifferent flocculation tailings materials. The floc breakdown pipelineassembly may have various configurations with different line lengths anddiameters, and may include a pipeline network with appropriate valvesand branches so as to provide a given desired pipe length and diameterto transport and condition a flow of flocculation tailings material to agiven deposition area or other dewatering unit.

In some implementations, the method of treating thick fine tailingsincludes: dispersing a flocculant into the thick fine tailings to form aflocculating mixture; shearing the flocculating mixture to increase ayield stress of the flocculating mixture and build up flocs, therebyproducing a flocculated mixture; shear conditioning the flocculatedmixture to decrease the yield stress of the flocculated mixture andbreak down flocs, wherein the shear conditioning is performed inaccordance with a pre-determined shearing parameter sufficient toproduce a conditioned flocculated material that is within a waterrelease zone wherein release water separates from the conditionedflocculated material; and dewatering the conditioned flocculatedmaterial while within the water release zone.

In some implementations, there is a method of determining shearconditioning for a flocculated thick fine tailings material to achievefloc breakdown and water release, including Camp Number scaling fromlaboratory scale mixer tests up to a commercial scale pipeline assembly.

The Camp Number scaling may include determining rheological behaviour ofa sample flocculated mixture comprising a sample of the thick finetailings and the flocculant in the laboratory scale mixer; determining alaboratory scale Camp Number sufficient to bring the sample flocculatedmixture within a water release zone in the laboratory scale mixer;determining the Camp Number so as to be substantially similar to thelaboratory scale Camp Number; and determining an equivalent pipe lengthand diameter for the pipeline assembly based on the Camp Number.

The sample flocculated mixture may be formed by rapid dispersion of theflocculant into the sample of thick fine tailings, and the floc build-upstage may be determined using empirical and/or CFD methods. The flocbuild-up stage may be determined based on reaching a peak yield stress,for example. The dispersion and floc-build-up stages may thus bepredicted for the up-scaled dewatering system. Thus, the dewateringsystem may be designed and controlled such that the floc build-uppipeline assembly downstream of the flocculant injection point impartssufficient shear to the flocculation tailings material to reach a peakyield stress and thus enter the floc breakdown stage upon reaching thefloc breakdown pipeline assembly that was designed based on the CampNumber for achieving the water release zone.

It should also be noted that the floc build-up assembly may include amixer, such as a tank impeller mixer, which imparts sufficient shear toincrease the yield stress of the flocculating mixture. The flocculatedmixture may then be withdrawn from the tank mixer and supplied to thefloc breakdown assembly, which may be a pipeline assembly. Thus, thefloc build-up and breakdown stages may be managed by variouscombinations of equipment, such as mixers and pipelines.

In some cases, the nature or properties of the source thick finetailings may change. In such cases, the rheological behaviour of theflocculation tailings material may also be affected, thus changing theshear requirements to achieve the water release zone. Othermodifications to the flocculating step (such as the use of a differentflocculant, a different flocculant solution or formulation and/orflocculant dosage) may also have the effect of altering the shearrequirements to achieve the water release zone. In such cases, themethod may include determining a new Camp Number and a newpre-determined amount of shear conditioning, which correspond to the newmodified flocculating characteristics; and imparting the newpre-determined amount of shear conditioning to the flocculated tailingsmaterial sufficient that the flocculated tailings material is within thewater release zone. The floc breakdown pipeline assembly may bere-configured to increase or decrease the equivalent pipe length and/ordiameter, as required, depending on the new Camp Number.

The step of determining rheological behaviour may include determining anoptimal flocculant dose range; adding the flocculant into a thick finetailings sample at the optimal flocculant dose range, to form a mixture;imparting dispersive mixing to the mixture in order to promotedispersion of the flocculant and floc build up; and imparting lowermixing to the mixture in order to further promote floc build up and tocommence floc breakdown until reaching the water release zone.

Determining rheological properties of the flocculation may be effectivesince different thick fine tailings, flocculant types, and flocculantdosages can result in different rheological behaviour of the flocculatedtailings. A sample of thick fine tailings may be obtained and tested inorder to determine an optimal flocculant dose, which may be on a claybasis. The flocculant dosage testing may involve conducting sweeps ofdifferent flocculant doses in a laboratory mixer and measuring therheological response of the flocculating mixture.

One test in this regard, which may be called the fast-slow mixer test,includes an initial stage of vigorous agitation (e.g., 320 rpm) of theflocculating mixture to simulate initial rapid dispersion of theflocculant into the tailings, followed by a stage of slower agitation(e.g., 100 rpm) to simulate the conditioning stage which may be done ina pipeline with lower shear levels compared to the dispersion stage.FIG. 8 shows an example of a test protocol for determining an optimalpolymer dose.

In addition to determining an optimal flocculant dose, determiningrheological properties of the flocculation may include determining therelationship between static yield stress and time in the mixer, as wellas determining the water release characteristics. The static yieldstress may be used as an indicator of the floc build-up and flocbreakdown stages. For example, the peak yield stress may be used as anapproximation of the end of the floc build-up stage and the onset of thefloc breakdown stage.

Some implementations provide a method of designing a pipeline assemblyfor transporting and conditioning a laminar flow of flocculated thickfine tailings material to a dewatering unit. The design method mayinclude subjecting a sample of flocculated thick fine tailings materialto shear and determining a sample shearing parameter comprisingresidence time and shear rate sufficient to bring the flocculated samplewithin a water release zone where release water separates from thesample; and configuring the pipeline assembly so as to have a pipelength and diameter providing a pipeline shearing parameter that issubstantially similar to the sample shearing parameter.

Some implementations provide a method of dewatering thick fine tailingsthat may utilize the design method described above. For instance, thedewatering method may include the steps of flocculating the thick finetailings to produce a flocculated thick fine tailings material; shearconditioning the flocculated thick fine tailings material in a pipelineassembly sized and configured according to a pipeline shearing parameterthat is substantially similar to a pre-determined sample shearingparameter comprising residence time and shear rate sufficient to bring asample of the flocculated thick fine tailings material within a waterrelease zone where release water separates from the sample, the pipelineassembly producing a conditioned flocculated material within the waterrelease zone; and dewatering the conditioned flocculated material whilewithin the water release zone. In some scenarios, the flow of theflocculated thick fine tailings material in a pipeline assembly has alaminar flow regime and the pre-determined shear parameter is a CampNumber.

In some implementations, there is a treatment system for treating thickfine tailings. The system may include a mixing device for mixing aflocculant into the thick fine tailings to form a flocculating mixture;a first shearing assembly for subjecting the flocculating mixture toshear to increase a yield stress of the flocculating mixture and buildup flocs, thereby producing a flocculated mixture; a pipelineconditioning assembly sized and configured for subjecting theflocculated mixture to an amount of shear conditioning in accordancewith a pre-determined shearing parameter sufficient to decrease theyield stress of the flocculated mixture and produce a conditionedflocculated material that is within a water release zone wherein releasewater separates from the conditioned flocculated material; and adewatering unit for receiving the conditioned flocculated material whilewithin the water release zone, for producing release water and dewateredtailings material.

While Camp Number scaling has been shown to be an efficient andeffective method of determining the configuration of the pipelineassembly for the thick fine tailings dewatering facility, it should alsobe noted that other shear parameters may be used in certaincircumstances. For example, a shear parameter that includes residencetime, shear rate and possibly other variables may be determined atlaboratory and/or pilot scale and used for scaling up to pipelineassemblies for larger dewatering operations. Additional variables mayinclude various other characteristics of the dewatering system and maybe empirically determined. Camp Number scaling has been shown to be arelatively simple and reliable method, but the scaling may be furtherrefined by adjusting a Camp Number-based shear parameter with additionalcomponents that may be related to the physico-chemical properties of thethick fine tailings, the flocculant, the flocculant solution and/orother constituents or properties of the dewatering system. For example,when additional in-line shear devices are provided as part of thetransportation and conditioning assembly, the Camp Number scaling may beadapted based on empirically derived constants or variables that dependon the given type of in-line shear device. Static mixers and tankimpeller mixers may impart the same average amount of shear to theflocculation tailings material, but the distribution of the shearimparted to the material may be slightly different due to constructionand operating differences between the two devices (e.g., dead zones mayexist in tank impeller mixers and thus a portion of the flocculationtailings material may experience less shear than the rest of thematerial). While other perhaps more complex shear parameters may be usedto scale the dewatering operations, the Camp Number has been shown to bean efficient and effective parameter.

In addition, when the flocculated thick fine tailings material in thefloc breakdown assembly has a laminar flow regime, the pre-determinedshear parameter may be a Camp Number. In other scenarios, when theflocculated thick fine tailings material has a turbulent and/ortransitional flow regime in the floc breakdown assembly, other shearparameters should be used for scaling.

In some implementations, the Camp Number scaling method may be used as amonitoring method for ongoing dewatering operations, in order to adjustor fine tune the process to maximize water release. For example, anexisting floc breakdown pipeline assembly may be brought offline andadjusted by adding or removing pipe section(s), thereby changing theoverall length of the floc breakdown pipeline assembly, in accordancewith a new laboratory Camp Number that was determined or estimated basedon the incoming thick fine tailings.

In determining the Camp Number or another shear parameter including ashear rate component, the shear rate may be taken as an average shearrate over the time interval. The average shear rate may be approximatedor estimated according to empirical correlations or other calculationmethods. The Camp Number may also be a composite of multiple Camp Numbercomponents obtained for a series of time increments, each having acorresponding shear rate or a corresponding average shear rate. The CampNumber components may be used for providing corresponding sections ofthe floc breakdown assembly.

Various aspects and implementations of the methods described herein willbe further understood in light of the following example section.

Examples, Experiments and Calculations

A mixer model was developed for a laboratory scale paddle mixer.Laboratory data has been obtained and compiled for many different typesof mature fine tailings having different characteristics, and includesrheological, dosage and water release capabilities of the tailingsmaterials.

A mixer model was developed with the data that had been obtained usingthe laboratory paddle mixer. The breakdown of the rheological propertiesof the flocs in the laboratory paddle mixer have been well characterizedto correlate with clay to water ratio (CWR). At the same time,laboratory test rig and field tests of pipe flow had exhibited similartrends in the rheological properties. However, in order to generate alaboratory mixer model, methods were developed to obtain theHerscehel-Bulkley fluid rheological properties of the treated MFT so arange of shear rates could be considered. This was successfullyperformed on two MFTs with identical properties to pressure tap trialsalong a pipeline test rig. It was clear there was a correlation betweenthe mixer and length of pipe required for flocculation in commercialapplication 12″ pipe and in the test rig 2″ pipe (26 meters and 4 metersrespectively, correlates to 30 seconds in the laboratory mixer). Theresults of the laboratory mixer allowed the understanding that the shapeof the pressure profiles downstream of the initial injection/mixingscaled with Camp Number (shear rate×time). Assuming sufficient initialmixing, the peak pressure drop occurs at substantially the same distancedownstream of the initial mixing independent of flow rate. This resultindicates that if sufficient initial mixing occurs, the breakdown offlocs can be accurately predicted using the Camp Number.

In one study, computational fluid dynamics (CFD) was used to analyzelaboratory data at different specific gravities and mixing speeds toascertain whether the change in rheological properties may be correlatedto absorbed energy.

Rheology of Treated MFT:

The first task in the analysis of paddle mixer data with treated MFT wasto characterize the rheological properties of the mixture. In paststudies—both with the laboratory paddle mixer and in pipe flow test—onlythe static yield stress was measured. However, to develop a comparativemodel between the paddle mixer data and pipe flow tests, the behavior ofthe mixture over a range of shear rates was preferred. This behavior canbe obtained from a Brookfield vane rheometer by measuring theTorque-Speed curve or flow curve.

FIG. 6 shows the geometry and stress profile in a large gap concentricsystem for a fluid with a yield stress. This system is an accuraterepresentation of the vane and cylinder system used in the laboratoryand field tests to measure the rheological properties of MFT andflocculant-MFT mixtures. When the vane rotates at constant angularvelocity Ω, the shear stress τ at the vane periphery (neglecting endeffects) is related to the torque T by:

$\begin{matrix}{\tau = {\frac{T}{2\pi\; R^{2}L} = \frac{2T}{\pi\; D^{2}L}}} & (1)\end{matrix}$

where R and D are the vane radius and diameter, respectively, and L isthe vane length. Now, the relationship between the angular velocity andthe shear rate γ is given by:

$\begin{matrix}{\Omega = {{\int_{R}^{R_{\gamma}}{\frac{\overset{.}{\gamma}}{r}{dr}}} = {\frac{1}{2}{\int_{\tau}^{\tau_{\gamma}}{\frac{f(\tau)}{\tau}\ d\;\tau}}}}} & (2)\end{matrix}$

and differentiating both sides of Eq. (2) with respect to τ, thefollowing direct relationship between angular velocity and shear rate isobtained:

$\begin{matrix}{\overset{.}{\gamma} = {\frac{2\Omega}{d\;\ln\;{\tau/d}\;\ln\;\Omega}.}} & (3)\end{matrix}$

From this basic information, a shear stress vs. shear rate curve can becalculated and then fit to a common non-Newtonian fluid model, such asthe Herschel-Bulkley equation of the form:τ=τ_(y) +k{dot over (γ)} ^(n)  (4)

where k is the consistency index, n is the power-law index and τ_(y) isthe yield stress. When the power-law index n=1, it reduces to theexpression for a Bingham plastic, as shown in FIG. 7. Note that the rawdata output from the Brookfield rheometer consists of the rotationalspeed N (in RPM) and the % torque T, so the actual torque can becalculated from:

$\begin{matrix}{T = {K_{s}{\frac{\overset{\_}{T}}{100}\left\lbrack {N - m} \right\rbrack}}} & (5)\end{matrix}$

where the spring constant Ks is given in Table 1. The rotational speedcan be converted to radians/second using:

$\begin{matrix}{\Omega = {\frac{2\pi\; N}{60}.}} & (6)\end{matrix}$

TABLE 1 Parameters of Brookfield Rheometer Spring Constant Model K_(s)HA 0.0014374 HB 0.0057496 RV 0.0007187 Vane Length Vane Diameter Vane cmcm V-71 6.878 3.439 V-72 4.338 2.167 V-73 2.535 1.267 V-74 1.176 0.589V-75 1.61 0.803

Paddle Mixer Analysis:

Paddle mixer experiments with two different MFT samples were conductedand rheological flow curves, as well as the static yield stress, weremeasured after approximately every 30 seconds of mixing. From each flowcurve, a shear stress vs. shear rate plot was calculated as describedabove and fit to a Herschel-Bulkley model. The first sample was Pond BMFT with a 47.21% solids content and 582 g/t of 0.45% polymer flocculantsolution. The mixing time, mixer speed, static yield stress and thecurve-fit coefficients for the Herschel-Bulkley model are given inTable 1. Then, using these curve-fit coefficients, a CFD model of thepaddle mixer was run to determine the torque on the paddle as well asthe shear rate, which are also tabulated in Table 1. Knowing the torqueand the mixer speed, the power P can be calculated from:P=TΩ.  (7)

The cumulative absorbed specific energy E is simply the power (per unitvolume) multiplied by the time in the mixer or:

$\begin{matrix}{E_{n} = {\sum\limits_{i = 1}^{n}{\frac{P_{i}\Delta\; t_{i}}{V}.}}} & (8)\end{matrix}$

where V is the paddle mixer volume. Lastly, the Camp Number may becalculated using the volume averaged shear rate G from the CFDsimulation and the incremental mixing time Δt according to:

TABLE 2 Treated MFT parameters for Pond 8A MFT in a paddle mixer. MixerStatic Cumulative Shear Mixing Speed Yield Torque, Power, Absorbed Rate,Time, N Stress τ_(y) k T P Energy, Ε G Camp t_(s) RPM Pa Pa n kgs^(n−3)/m mN-m W W-h/m³ s⁻² No. 0 — 7.13 — — — — — — — — 9 320 515.1069.0 0.345 10.68 46.98 1.574 13.02 43.06 387.56 20 320 171.09 44.9 0.4086.29 36.13 1.211 25.27 44.94 494.33 50 100 104.16 32.1 0.619 3.70 21.370.224 31.44 13.18 395.52 80 100 61.30 25.6 0.619 3.41 18.16 0.190 36.6813.27 397.99 110 100 51.90 23.2 0.772 2.99 21.37 0.224 42.85 13.88410.30 140 100 47.66 25.4 0.879 2.15 22.94 0.240 49.48 13.78 413.43

The results of a similar analysis for a Pond D 22% solids by weight(SBV) MFT with 896 g/t of 0.45% polymer solution are given in Table 3.

TABLE 3 Treated MFT parameters for STP 22% SBW MFT in a paddle mixer.Static Cumulative Mixing Mixer Yield Absorbed Shear Time Speed Stressτ_(y) k Torque Power Energy Rate Camp _(s) RPM Pa Pa n kg s^(n−3)/m mN-mW W-h/m³ s⁻¹ No. 0 — 1.98 — — — — — — — — 20 320 165.80 39.3 1.0 0.04025.90 0.868 15.96 48.75 975.10 50 100 88.58 30.3 1.0 0.121 13.45 0.14119.84 12.73 381.85 80 100 68.78 26.7 1.0 0.140 12.29 0.129 23.39 12.81384.44 110 100 53.37 22.1 1.0 0.153 10.66 0.112 26.47 12.94 388.09 140100 40.00 19.4 1.0 0.149 9.58 0.100 29.23 13.01 390.18 170 100 33.8016.3 1.0 0.165 8.53 0.089 31.70 13.16 394.75

The static yield stress is always considerably higher than the yieldstress obtained from the shear stress-shear rate plots, since the vaneis not rotating at constant speed for rheometer test. It is alsointeresting to note that the Camp Number for both paddle tests weresimilar in magnitude and, in addition, the cumulative absorbed energy atthe point which the static yield stress starts to decline dramaticallywas similar in magnitude—about 20 W-h/m³—to the measurements made byPornillos.

The mixer cylinder diameter was 10.5 cm and the paddle dimensions were7.62 cm×2.54 cm; the total MFT volume was about 300 mL.

Pipe Flow Analysis:

The two different MFT samples were similar to the MFT used in thededicated disposal area (DDA) commercial scale tests conducted in 12″pipe and the laboratory rig tests conducted in 2″ pipe, respectively.For both of these MFT samples, the rheological parameters determinedfrom the paddle mixing experiments were input to a CFD model of a pipewith periodic boundary conditions, from which the pressure gradient andvolume averaged shear rate were determined. From the calculated valuesof average shear rate, the equivalent length of pipe was determined toprovide the same Camp Number. The results are tabulated in Tables 4 and5.

Based on the results in Tables 4 and 5, there is a correlation betweenthe time increment in the mixer and the length of pipe required toprovide the same shear experience: for the 12″ pipe, a length of about26 m is equivalent to 30 seconds in the paddle mixer. In addition, thislength is substantially independent of flow rate since at lower flowrates the shear rate is lower, but so is the speed so it takes a longertime to reach the same distance downstream. Likewise, at higher flowrates the shear rate is higher, but due to the higher speed, it takesless time to reach a particular distance downstream. Camp Number scalinghas been demonstrated for this application.

For the DDA tests, the discharge location was about 80 meters downstreamof the injection point. Disregarding the initial mixing right after theinjector, the shear experience of the treated MFT at the exit of thepipe would be roughly equivalent to 80 seconds in the paddle mixer,based on the required pipe length to produce the same Camp Number. Inlaboratory paddle mixing tests, this amount of mixing has been shown tocorrespond approximately to the optimum mixing for maximum dewatering.In the DDA tests, it was observed that better water release was observedat higher tailings flow rates (>550 m³/h) while at lower flow rates(350-450 m3/h) there seemed to be too little initial mixing of thepolymer, which reduced subsequent water release. However, in thosetests, the initial injection mixing was not independent of the flowrate: the higher the flow rate, the better the initial mixing. Themeasured pressure gradient along the 12″ pipe for the lowest polymerdosage at 550 m³/h varied between 1100-1900 Pa/m, which is close to thesame range predicted by the CFD results (see Table 4).

In another laboratory test, the initial injection mixing was set at arelatively high flow rate and then the flow rate through an instrumenteddownstream section was varied using a diversion valve. In this manner,lower flow rates in the downstream section were not subject to lessinitial mixing. The results of the laboratory test showed that the shapeof the pressure profiles downstream of the initial injection mixingscaled with Camp Number, showing that the peak pressure drop occurs atthe same distance downstream of the initial mixing. This resultindicates that if sufficient initial mixing occurs, the degradationdownstream can be accurately predicted using the Camp Number.

TABLE 4 Treated MFT parameters for Pond 8A MFT in a 12″ pipe at 550m^(3/)h. Mixer Static Pressure Mixing Speed Yield Shear Pipe Gradient,Time, N Stress τ_(y) k Camp Rate, G Length dP/dx t_(s) RPM Pa Pa n kgs^(n−2)/m No. s⁻¹ m Pa/m 9 320 515.10 69.0 0.345 10.68 387.58 30.0726.99 2190.17 20 320 171.09 44.9 0.408 6.29 494.33 30.17 34.31 1732.7650 100 104.15 32.1 0.619 3.70 395.52 31.14 26.60 1990.78 80 100 61.3025.6 0.619 3.41 397.99 31.13 26.77 1823.34 110 100 51.90 23.2 0.772 2.99410.30 32.00 26.84 2312.44 140 100 47.66 25.4 0.879 2.15 413.43 32.2726.82 2494.82

For the 2″ pipe, a length of 4 m is roughly equivalent to 30 seconds inthe paddle mixer (see Table 5). For the 2″ pipe tests in the laboratoryscale rig, it was observed that the MFT was oversheared at the pipeexit, which was about 16 m from the polymer injection location. If theinitial mixing is disregarded, the shear experience of the treated MFTat the exit of the pipe would be roughly equivalent to 140 seconds inthe paddle mixer, based on the required pipe length to produce the sameCamp Number. Again, based on laboratory paddle mixing tests, this amountof mixing has been shown to correspond to an oversheared case, which wasindeed observed in the pipe test rig experiments.

TABLE 5 Treated MFT parameters for STP 22% SBW MFT in a 2″ pipe at 30LPM. Mixer Static Pressure Mixing Speed Yield Shear Pipe Gradient, Time,N Stress τ_(y) k Camp Rate, G Length dP/dx t_(s) RPM Pa Pa n kgs^(n−3)/m No. s⁻¹ m Pa/m 20 320 165.80 39.3 1.0 0.040 975.10 20.62 11.663697.52 50 100 88.58 30.3 1.0 0.121 381.85 21.41 4.40 3301.99 80 10068.76 26.7 1.0 0.140 384.44 21.64 4.38 3050.79 110 100 53.37 22.1 1.00.153 388.09 21.90 4.37 2674.87 140 100 40.00 19.4 1.0 0.149 390.1822.01 4.37 2408.43 170 100 33.80 16.3 1.0 0.165 394.75 22.30 4.372171.42

Correlation Model:

In order to utilize the paddle mixer data for pipe flow predictions, thefollowing procedure may be implemented:

-   -   1. For a particular thick fine tailings type and polymer        flocculant dosage, measure the rheology flow curves for various        mixing times of the typical paddle mixer experiments, as        presented in Tables 2 and 3 (e.g., build up a data base of        Herschel-Bulkley coefficients and correlate the data with        optimal water release characteristics).    -   2. Determine the Camp Number for the various mixing times from        CFD of the paddle mixer (e.g., characterize the mixer shear rate        without having to do a CFD run at each different set of        Herschel-Bulkley coefficients).    -   3. Determine the equivalent pipe length L_(eq) from a pipe shear        rate estimate using a particular set of Herschel-Bulkley        coefficients (from a point in the paddle mixing curve that is        after the peak yield stress).    -   4. Split the discharge pipe of length L into n=L/L_(eq) segments        so that each segment is roughly equivalent to the mixing time        increments of the paddle mixer curve.    -   5. Calculate the ΔP for each segment L_(eq) by applying the        appropriate Herschel-Bulkley coefficients for that segment.

An alternative to Steps 4 and 5 is to determine what pipe length isrequired for the particular MFT-polymer flocculant mixture to obtainoptimum water release without overshearing (i.e., instead of calculatingthe pressure drop along a given length). With correct Camp Numberscaling, there will be an optimum pipe length for a particular MFT,regardless of flow rate, if there is sufficient initial mixing at thepolymer flocculant injection location.

In order to make the pipe flow predictions outlined in the aboveprocedure, expressions for the pressure drop and average shear rate forthe laminar flow of a Herschel-Bulkley fluid can be used. The followingexpressions for the velocity profile have been derived in theliterature:

For 0<r>r_(y)U=U _(c).  (10)

For r_(y)<r>R

$\begin{matrix}{\mspace{79mu}{U = {{U_{c}\left( {1 - \left( \frac{r - r_{y}}{R - r_{y}} \right)^{\frac{n + 1}{n}}} \right)}.}}} & (11)\end{matrix}$

The center-line velocity U_(c) is given by:

$\begin{matrix}{\mspace{79mu}{U_{m} = {\left( {{- \frac{1}{2k}}\frac{dP}{dx}} \right)^{\frac{1}{n}}\left( \frac{n}{n + 1} \right)\left( {R - r_{y}} \right)^{\frac{n + 1}{n}}}}} & (12)\end{matrix}$

and the mean velocity U_(m) is:

$\begin{matrix}{\mspace{79mu}{U_{m} = {{U_{c}\left( {1 - {\frac{2n}{R^{2}}\frac{\left( {R - r_{y}} \right)^{2}}{\left( {{3n} + 1} \right)}} - {\frac{2n}{R^{2}}\frac{\left( {R - r_{y}} \right)}{\left( {{2n} + 1} \right)}r_{y}}} \right)}.}}} & (13)\end{matrix}$

The yield radius ry is obtained from a force balance on the centralcore:

$\begin{matrix}{r_{y} = {\frac{2\tau_{y}}{{dP}/{dx}}.}} & (14)\end{matrix}$

Now, the literature gives the following equation for the pressuregradient:

$\begin{matrix}{\frac{dP}{dx} = {\frac{4k}{D}\left( \frac{8U}{C} \right)^{''}\left( \frac{{3n} + 1}{4n} \right)^{''}\left( \frac{1}{1 - X} \right)\left( \frac{1}{1 - {aX} - {bX}^{2} - {cX}^{3}} \right)^{''}}} & (15)\end{matrix}$

where X is given by

$\begin{matrix}{X = {\frac{\tau_{y}}{\tau_{w}} = {\frac{4\tau_{y}}{D\;{{dP}/{dx}}}\mspace{14mu}{and}}}} & (16) \\{{a = \frac{1}{{2n} + 1}};{b = \frac{2n}{\left( {n + 1} \right)\left( {{2n} + 1} \right)}};{c = {\frac{2n^{2}}{\left( {n + 1} \right)\left( {{2n} + 1} \right)}.}}} & (17)\end{matrix}$

Finally, the average shear rate G can be calculated by integrating thevelocity gradient ∂U ∂r across the sheared region:

$\begin{matrix}{G = {{- \frac{1}{A}}{\int_{r_{y}}^{R}{\frac{\partial U}{\partial r}2\pi\;{rdr}}}}} & (18)\end{matrix}$

where A is either the entire pipe cross-sectional area or just thecross-sectional area of the sheared region, i.e.:A=πd ² or A=π(R ² −r _(y) ²)  ((19)the only difference is whether the shear rate is averaged over the wholepipe or just the sheared area. Regardless, from Eq. (11):

$\begin{matrix}{\frac{\partial U}{\partial r} = {\frac{n + 1}{n}\frac{- U_{c}}{\left( {R - r_{y}} \right)^{\frac{n + 1}{n}}}\left( {r - r_{y}} \right)^{\frac{1}{n}}}} & (20)\end{matrix}$

and Eq. (18) becomes:

$\begin{matrix}{G = {\left( {{- \frac{1}{2k}}\frac{dP}{dx}} \right)^{\frac{1}{n}}\frac{2\pi}{A}{\int_{r_{y}}^{R}{{r\left( {r - r_{y}} \right)}^{\frac{1}{n}}{dr}}}}} & \left( {18a} \right)\end{matrix}$

which, upon integration, becomes:

$\begin{matrix}{\left. {G = {\left( {{- \frac{1}{2k}}\frac{dP}{dx}} \right)^{\frac{1}{n}}\frac{2\pi}{A}\left( {r - r_{y}} \right)^{\frac{1 + n}{n}}\left( {\frac{r - r_{y}}{2 + \frac{1}{n}} + \frac{r_{y}}{1 + \frac{1}{n}}} \right)}} \right\rbrack_{r_{y}}^{R}\mspace{14mu}{or}} & \left( {18b} \right) \\{G = {\left( {{- \frac{1}{2k}}\frac{dP}{dx}} \right)^{\frac{1}{n}}\frac{2\pi}{A}\left( {R - r_{y}} \right)^{\frac{1 + n}{n}}{\left( {\frac{R - r_{y}}{2 + \frac{1}{n}} + \frac{r_{y}}{1 + \frac{1}{n}}} \right).}}} & \left( {18c} \right)\end{matrix}$

With these analytical expressions, the pipe flow predictions outlined inSteps 1 to 5 above can be carried out in a piece-wise fashion along thedischarge pipe using the rheology measurements obtained with the paddlemixer at various mixing times.

Net Water Release and Flocculant Dosage:

It should also be noted that the water release zone and the flocculantdosage may be determined according to various methods. In somescenarios, the Net Water Release (NWR) may be measured for the sampleflocculated tailings.

NWR is a metric that has been developed and is a measure of thedifferential in water between the starting thick fine tailings and thetreated and drained thick fine tailings after a given draining time. Inother words, NWR is a difference in moisture contents. The draining timemay be 24 hours, 12 hours, 20 minutes, or 19 minutes, for example, oranother representative time period for drainage in commercialapplications. There are two main ways to calculate the NWR by volumetricor solid content difference. Example formula to calculate the NWR are asfollows:

$\mspace{20mu}{{NWR} = \left( \frac{\begin{matrix}{{{Quantity}\mspace{14mu}{of}\mspace{14mu}{water}\mspace{14mu}{Recovered}} -} \\{{Quantity}\mspace{14mu}{of}\mspace{14mu}{Flocculant}\mspace{14mu}{Water}\mspace{14mu}{Added}}\end{matrix}}{{Quantity}\mspace{14mu}{of}\mspace{14mu}{intial}\mspace{14mu}{Fine}\mspace{14mu}{Tailings}\mspace{14mu}{Water}} \right)}$${NWR} = {1 - {\left( \frac{1}{{{tMFT}\mspace{14mu}{wt}\mspace{14mu}\%\mspace{14mu}{mineral}} + {{wt}\mspace{14mu}\%\mspace{14mu}{Bitumen}} - 1} \right) \div \left( \frac{1}{{{MFT}\mspace{14mu}{wt}\mspace{14mu}\%\mspace{14mu}{mineral}} + {{wt}\mspace{14mu}\%\mspace{14mu}{Bitumen}} - 1} \right)}}$

A NWR test may be conducted using immediate drainage of a flocculationtailings sample for a drainage time of about 20 minutes. In this regard,for optimal dosage range and good flocculation, the water release in 10or 20 minutes may be about 80% of the water release that would occurover a 12 to 24 hour period. For underdosed or overdosed samples, thewater release in 20 minutes may be about 20% to 60% of the water releasethat would occur over a 12 to 24 hour period. The 20 minute NWR test maytherefore be followed by a longer NWR test, e.g. 12 hour drainage time,which may use a water volume or solids content measurement approach. Itis also noted that the laboratory and filed tests described herein useda volumetric 24 hour NWR test. A greater initial water release resultsin a shorter drying duration that is required to achieve a certainsolids target. The NWR is dependent on several factors, including thedispersion of the flocculant into the thick fine tailings and thesubsequent conditioning (including mixing) of the flocculation tailings.Rapid and thorough dispersion is preferred for increasing NWR.

Another test method includes determining optimal flocculant dosageranges for flocculating and dewatering the thick fine tailings. Ingeneral, the flocculant dosage testing may include determining an amountof the flocculating agent required to transformed a sample of the thickfine tailings into a sample flocculation tailings having a positivemeasured Net Water Release (NWR) in response to shear conditioningbeyond a peak static yield stress. In particular, the dosage testing mayinclude a dose find test (Phase I) and a dose sweep test (Phase II). ThePhase I test may include incremental addition of an amount of flocculantto the sample of thick fine tailings until flocculation and waterrelease are observed. For example, 1 to 5 ml of flocculant solution maybe incrementally added to the thick fine tailings sample. The sample issubjected to mixing during the flocculant addition, which may beconstant rotations per minute of an impeller mixer blade. Each incrementof flocculant is well mixed into the sample before adding the nextamount of flocculant. Incremental addition may be viewed as a titrationto determine an approximate dosage of flocculant for flocculating thegiven sample and achieving a water release zone. The incrementaladdition is repeated until a change in the structure of the sample andwater release is observed. The water release may be measured by variousmeans, including one of the NWR tests described herein and/or aCapillary Suction Time (CST) test. The Phase II test may be conductedwhere the flocculant for a given approximate dosage (e.g. determined inPhase I or previously estimated from data sets) is injected all at once.The flocculant may be added to a thick fine tailings sample and then thesample may be subjected to mixing, which may be a two stage mixing ofrapid shear mixing to induce dispersion of the flocculant into thesample followed by a slower mixing to shear condition the flocculationsample until it reaches the water release zone. NWR may be determinedfor each dosage of the sweep. For example, dosages 100 PPM either sideof the approximate dosage from Phase I may be determined to produce adosage curve for each sample (e.g., NWR vs dosage). Additional dosagesbeyond those may also be tested to provide a more complete curve. ThePhase II dose results may be a reasonable indicator of the dosagerequirements in up-scaled commercial application of flocculation anddewatering operations. Thus, the flocculant dosage test may includeconducting a first dosage test (e.g., Phase I) to identify an initialdosage approximation at which positive NWR occurs and a second dosagesweep test (e.g., Phase II) to determine variation of NWR as a functionof dosage of flocculating agent around the initial dosage approximation.The next step may include determining a revised dosage in accordancewith a maximum NWR range or value from the dose sweep test. The dosagegiving the maximum NWR value may also be extrapolated from the dosagesweep curve if it appears that the maximum dosage would be between twoadjacent doses that were actually tested. The revised dosage can then beused for implementing and/or adjusting a flocculation and dewateringoperation. Optionally, as illustrated in FIG. 8, the dosage test (e.g.,Phase I) and the dosage sweep test (e.g., Phase II), may be followed byfull characterization tests (e.g., Phase III) and/or a standard dryingtest (e.g., Phase IV). The full characterization tests (e.g., Phase III)allow the determination of the water release, YS, viscosity and/or CSTin different mixing zones. A single injection may be used. The standarddrying test (e.g., Phase IV) allows the determination of the effect ofdose and water release on drying rates and rheology.

It should be noted that various implementations, aspects and embodimentsdescribed herein may be combined with other implementations, aspects andembodiments described herein.

The invention claimed is:
 1. A method of dewatering thick fine tailings,comprising: flocculating the thick fine tailings to produce aflocculated thick fine tailings material; flowing the flocculated thickfine tailings material in a pipeline assembly under a laminar flowregime to shear condition the flocculated thick fine tailings materialand break down flocs, the pipeline assembly having a pipe length anddiameter sized substantially independent of flow rate of the flocculatedthick fine tailings material and according to a pre-determined pipelineshearing parameter determined under laminar conditions and comprisingresidence time and shear rate, the pipeline assembly producing aconditioned flocculated material within a water release zone; anddewatering the conditioned flocculated material while within the waterrelease zone.
 2. The method of claim 1, wherein the flocculating step isperformed in-line and comprises dispersing a flocculant into the thickfine tailings to form a flocculating mixture and shearing theflocculating mixture to build up flocs and produce the flocculated thickfine tailings material.
 3. The method of claim 1, wherein only aflocculant is added into the thick fine tailings prior to thedewatering.
 4. The method of claim 1, wherein the pre-determinedshearing parameter is a pre-determined Camp Number.
 5. The method ofclaim 4, wherein the pre-determined shearing parameter is determined bymixing a flocculant with a sample thick fine tailings for producing asample flocculating mixture under turbulent conditions to form a sampleof the flocculated thick fine tailings material having a peak yieldstress, and then shearing the sample of the flocculated thick finetailings material under laminar conditions until the water release zone.6. The method of claim 1, wherein the dewatering comprises depositingthe conditioned flocculated material onto a sub-aerial deposition area.7. The method of claim 1, wherein the dewatering comprises drainingwater away from solid flocculated material.
 8. The method of claim 1,wherein the dewatering comprises subjecting the conditioned flocculatedmaterial to thickening.
 9. The method of claim 8, wherein the thickeningis performed in a thickener unit that produces a thickened underflow andan overflow.
 10. The method of claim 1, wherein the dewatering comprisessubjecting the conditioned flocculated material to filtration.
 11. Themethod of claim 1, wherein the dewatering comprises supplying theconditioned flocculated material to a separation unit.
 12. A method ofdewatering thick fine tailings, comprising: adding a flocculant into thethick fine tailings to produce a flocculation tailings material; shearconditioning the flocculation tailings material in a pipeline assemblyto produce a conditioned flocculated material within a water releasezone wherein release water separates from the conditioned flocculatedmaterial; providing sufficient mixing of the flocculant and the thickfine tailings prior to the shear conditioning, so as to enable thepipeline assembly to have a pipe length based on Camp Number scaling toachieve the water release zone; and dewatering the conditionedflocculated material within the water release zone to produce adewatered tailings material and release water.
 13. The method of claim12, wherein the step of adding the flocculant is performed in-line andunder turbulent flow conditions.
 14. The method of claim 12, wherein thestep of providing sufficient mixing is performed in-line, and toincrease a yield stress of the flocculation tailings material to a peakyield stress.
 15. The method of claim 12, wherein the step of providingsufficient mixing comprises subjecting the flocculation tailingsmaterial to turbulent flow conditions to build up flocs until reachinglaminar flow conditions prior to the shear conditioning.
 16. The methodof claim 12, wherein the Camp Number scaling comprises: mixing a sampleof the thick fine tailings with the flocculant under turbulentconditions to produce a sample flocculated mixture; shearing the sampleflocculated mixture under laminar conditions to determine a Camp Numberfor achieving the water release zone in the sample; and providing thepipeline assembly with a length and a diameter for providing theflocculating tailings material with an amount of shear according to theCamp Number.
 17. The method of claim 16, wherein the mixing of thesample of the thick fine tailings with the flocculant and/or theshearing of the sample flocculated mixture is performed in a laboratoryscale mixer.
 18. The method of claim 12, wherein the pipeline assemblycomprises at least one in-line shear device having an equivalent pipelength.